Sergei Kiriyenko, general director of Rosatom, the Russian State Atomic Energy Corporation said Saturday's arrival of nuclear fuel marks "an event of crucial importance" that proves that "Russia always fulfills its international obligations."

Spent nuclear fuel from the plant will be sent back to Russia.

The opening of the plant prompted the White House to question Iran continuing to enrich uranium within its borders.

"Russia is providing the fuel, and taking the fuel back out," White House spokesman Robert Gibbs said earlier this month.

"It, quite clearly, I think, underscores that Iran does not need its own enrichment capability if its intentions, as it states, are for a peaceful nuclear program," he said.

Russian Foreign Minister Sergey Lavrov, speaking to Russian reporters in the Black Sea resort of Sochi Wednesday, brushed off Western concerns about the Bushehr facility, calling it "the most important anchor holding Iran to the nonproliferation regime," according to the Russian news agency RIA-Novosti.

Alistair Burt, Britain's foreign minister, said on Saturday the development "demonstrates that Iran can have the benefits of nuclear power."

"The problem is Iran's continued refusal to satisfy the IAEA and international community that its work on uranium enrichment and heavy water projects are exclusively peaceful."

The Bushehr facility was originally scheduled to start operations in 2007, but the date for commissioning the plant has been postponed a number of times due to various technical, financial and political factors.